Project Summary: Improved survival in persons living with HIV (PLWH) has led to a higher prevalence of several chronic illnesses including chronic obstructive pulmonary disease (COPD), which affects an estimated 3-23%. A major gap in knowledge is the inability to identify those at risk and a limited understanding of why HIV increases COPD risk independent of smoking status. In our recent published report, we identified 172 unique plasma analytes that differentiated HIV+ individuals with COPD compared to their HIV+ matched controls. We identified 17 of these metabolites to be lipids by LC-MS/MS, including diacylglycerol and several sphingolipids. Sphingolipids are important participants in cell signaling and function as a rheostat balancing cell proliferation, pro- and anti- apoptotic states and the inflammatory process. In HIV negative individuals with COPD, sphingolipids, particularly ceramide, are linked to COPD pathogenesis and serve as putative biomarkers of disease. We propose to build upon our previous work and leverage our sample repositories to define the molecular signature of PLWH en route to developing COPD and uncover underlying mechanisms of disease. We hypothesize that a unique lipid biosignature is associated with HIV-COPD susceptibility in PLWH and is directly linked to pathogenesis. In this proposed research project, we will use state-of-the-art metabolomic and proteomic approaches to determine the relationship between lipid profiles with accelerated lung function decline in HIV. Our research takes advantage of our team's expertise (biomarker discovery in COPD; metabolomics and computational analysis; COPD in HIV infection) and the unique opportunity presented by the Pittsburgh Lung HIV, Vancouver Lung HIV and Strategic Timing of Antiretroviral Treatment (START) cohorts. Our first approach is to identify lung specific lipid profiles associated with HIV-COPD using bronchoalveolar lavage (BAL) samples from the well-phenotyped Pittsburg and Vancouver cohorts. We anticipate from our published work that many of the plasma lipids associated with HIV-COPD will be lung specific. To unravel key canonical pathways and biological processes linked to HIV-COPD we will employ a hypothesis-driven proteomic-based approach comprising data-independent acquisition mass spectrometry (DIA-MS) with Sequential Windowed Acquisition of All Theoretical Fragment Ion Mass Spectra (SWATH-MS) of BAL, with data analysis including gene ontology. Downstream signaling pathways of sphingolipids, such as cell proliferation, pro- and anti-apoptotic states and the inflammatory process, will serve as our hypothesis-driven focus. We will then validate lung specific lipid profiles that are present in plasma and predict accelerated lung function decline using plasma samples from the 1,026 START subjects in our longitudinal spirometry substudy.